DMVPN hierarchical topology
DMVPN can be employed using a hierarchical topology. In such a topology, there are multiple levels of DMVPN hubs. This means that a spoke can also be a hub to additional sub-spokes.
A hierarchical DMVPN topology can sometimes be considered as a third DMVPN topology, such as DMVPN dual hub dual cloud and DMVPN dual hub single cloud.
A hierarchical DMVPN topology requires the use of DMVPN Phase 3.
Links:
https://forum.networklessons.com/t/dmvpn-phase-3-basic-configuration/1311/43?u=lagapides